1. Field of the Invention
The present invention relates to a method of and apparatus for gripping corners of strips of cloth which may be applied to, for example, systems for spreading strips of cloth, systems for sorting linens or other textile products, and systems for spreading linens or the like before they are washed.
2. Description of the Related Art
Generally speaking, in laundry works, received goods such as sheets, towels and wrapping cloth (hereinafter referred to as "strips of cloth") are washed in a continuous washing machine or the like and then dewatered before being cast into a drier. Strips of cloth which have been subjected to the drying process are disentangled and spread. Then, the strips of cloth are ironed and folded for forwarding. In this series of processes, between the drying process and the ironing process, strips of cloth taken out of the drier are transported to a predetermined place by means of a belt conveyor, and five to six operators take out strips, one by one, from a mass of cloth which is stacked, and they spread the strips of cloth and feed them to an ironing device or an auxiliary device thereof (e.g., a spreader, a feeder, etc.).
Spreading of strips of cloth finished with the drying process involves an operation conducted in an atmosphere of high temperature and humidity, which means that the operators suffer from heavy labor in the inferior environment. In these circumstances, it has heretofore been demanded to develop an apparatus which enables automation of the operation of spreading strips of cloth. However, such automated apparatus is not present in the art, and there is only one related art which is a method of holding a strip of cloth in a fixed position, disclosed in Japanese Patent Publication No. 59-24685 (1984).
This prior art method comprises: a first step of suspending a strip of cloth by holding one portion thereof; a second step of holding the lowermost corner portion of the strip suspended in the first step and releasing the strip from the hold made in the first step; a third step of holding the lowermost end portion of the strip suspended in the second step; and a fourth step of stretching the strip while holding substantially horizontal the section of the strip between the two points held in the second and third steps. For the case of a rectangular strip of cloth, the following description is set forth in the specification of the prior art.
Namely, when, in the first step, a rectangular strip S of cloth is suspended by holding it at any one point, the straight line which intersects the held point 27 and the center of gravity 28 is vertical as shown in FIG. 42. When, in the second step, the lowermost corner 29 of the strip S in this state is held to suspend the strip S and further the strip S is released from the hold made in the first step, the distance between the upper and lower corners 29 and 30 is constant as shown in FIG. 43. Therefore, in the third step the lower corner 30 of the strip S as viewed in FIG. 43 is held. Then, in the fourth step, the upper and lower corners 29 and 30 which are points held in the second and third steps, respectively, are held so that the section between these points is substantially horizontal as shown in FIG. 44. Thus, the strip S is held in a fixed position and may be transferred to a subsequent process. To hold the strip S in a spread state, either one of the lower corners 31 and 32 shown in FIG. 44 is held in the fifth step.
FIG. 45 is a front view of an apparatus for holding a strip of cloth in a fixed position which may be employed to carry out the above-described method. For the convenience of description, the apparatus is divided into four sections A to D. The apparatus is arranged as follows. In the section A, a strip of cloth is held and one corner of the strip which is held is detected; in the section B, a corner opposing the corner held in the section A is detected; in the sections B and C, the strip which is held at opposing corners thereof is held so that the diagonal line is horizontal, and either one of the corners which define the lower ends and which overlap each other is held; and in the sections C and D, corners of the strips which are adjacent to each other are held and the strip is thus held in a fixed position. In the figures, a squeezing rod 70 is provided in the vicinity of the extremity of the rightward movement of a chuck 68 in such a manner that the rod 70 is vertically movable along a guide slot 71.
A chuck 72 is provided below the extremity of the rightward movement of the chuck 68 in such a manner that the chuck 72 is vertically movable along a guide slot 73 and also movable rightwardly upward from its top dead center. A squeezing rod 74 is provided in the vicinity of the top dead center of the obliquely vertical movement of the chuck 72 in such a manner that the rod 74 is vertically movable along a guide slot 75. A chuck 76 is provided in such a manner as to be movable in the obliquely vertical direction, the bottom dead center of the chuck 76 being set below the top dead center of the obliquely vertical movement of the chuck 72. A chuck 78 is provided in such a manner as to move vertically along a guide slot 79 below the medium point of the line which intersects the respective top dead centers of the obliquely vertical movements of the chucks 72 and 76 and further in such a manner that the chuck 78 moves in the obliquely vertical direction with its top dead center defined as the bottom dead center of its obliquely vertical movement. It should be noted that the chucks 68, 72, 76, 78 and the squeezing rods 70 and 74 are driven by means of air cylinders (not shown) so as to move along the respective guide slots.
With this apparatus, a rectangular strip of cloth is held in a fixed position according to the following procedure. Referring first to FIG. 46, a portion of a strip 80 of cloth which is to be held in a fixed position is detected and held by the chuck 68, and the chuck 68 rises along the guide slot 69 and then moves rightward, thus bringing the strip 80 into the state shown in FIG. 47. Referring to FIG. 47, the strip 80 which is suspended from the chuck 68, since its lowermost corner is not necessarily disposed directly above the chuck 72, is squeezed with the squeezing rod 70, which is circular and has a notch in part thereof, so that the lowermost corner of the strip 80 comes directly above the chuck 72 located directly below the chuck 68. Thereupon, the chuck 72 moves upward and holds one of the corners of the rectangle which defines the lowermost corner of the strip 80 as shown in FIG. 48. Thereafter, the chuck 68 releases the strip 80, and the chuck 72 moves downward and further moves rightwardly upward along the guide slot 73. At this time the squeezing rod 70 returns to the top dead center of the guide slot 71.
Referring to FIG. 49, the strip 80 which is suspended from the chuck 72 and which has reached the top dead center of the guide slot 73 and faces downward is squeezed with the squeezing rod 74. In consequence, the lowermost corner (the corner opposing the corner held by the chuck 72) of the strip 80 comes to the position of the chuck 76 (a fixed position determined in accordance with the size of the strip 80) and therefore is detected and held by the chuck 76. The chuck 76 holding the lowermost corner of the strip 80 rises along the guide slot 77 to the top dead center, so that the two opposing corners of the strip 80 are held horizontal by means of the chucks 72 and 76 as shown in FIG. 50. At this time, the squeezing rod 74 returns to the top dead center of the guide slot 75.
Referring next to FIG. 50, the strip 80 is held by the chucks 72 and 76 so that the two opposing corners are horizontal. Then, the strip 80 can be held in a fixed position in such a manner that its adjacent corner is held by providing a chuck 81 corresponding to the chuck 76 at the position of either one of the two suspended corners of the strip 80, holding said suspended corner with the chuck 81, opening the chuck 72, and holding the strip 80 with the chucks 76 and 81. It should be noted that, since in this apparatus the distance between the right upper end position of the chuck 72 and the left bottom end position of the chuck 76 is set so as to be substantially equal to the length of the diagonal line of strips which are to be handled, when the chuck 72 holds two corners of the strip 80 which are adjacent to each other in the step shown in FIG. 48, the chuck 76 cannot hold the strip 80, and therefore the strip 80 must try to be held again.
The apparatus for gripping a strip of cloth which is employed in the above-described conventional apparatus has the following problems.
Namely, since the chucks 72, 76 and 81 are located in their respective fixed positions, it is only possible to spread rectangular strips of cloth having specific dimensions, and therefore the apparatus is not practical with respect to strips of cloth having diverse dimensions.
Further, since the chuck 72 cannot move from its fixed position before the chuck 81 holds the strip 80 of cloth, it is necessary in order to spread the strip 80 at high speed to provide a plurality of apparatuses of the same arrangement, which means that the spreading ability is disadvantageously low.